Web structures can be used in the formation of tires to provide part of the carcass structure of the tire or as other reinforcement of the tire. A web structure typically includes a plurality of metallic cables arranged approximately mutually parallel with one another with a given transverse pitch. The metallic cables are typically embedded in a viscoelastic material, such as a rubber material.
A typical process that is used to manufacture web structures includes depositing a layer of rubber material on both sides of a plurality of metallic cables using a calender formed from two rolls capable of pressing heated rubber sheets against each other. The rubber sheets are heated to a temperature sufficient to allow the rubber sheets to be pressed together and to cover the plurality of metallic cables to form the metallic web structure.
Given the high speeds at which the web structures are formed during the calendering process, anomalies can occur in the web structure as it is being manufactured. For instance, a web structure can include a portion having a missing metallic cable due to failure of the metallic cable to be properly fed into the calender. In addition, a web structure can include an out of place metallic cable, such as a cable that is not sufficiently spaced from neighboring cables. As another example, the rubber material can be missing over a portion of the metallic cables, leaving a portion of the metallic cables of the web structure exposed.
Another anomaly that can occur includes an improper web trim along the side edges of the web structure. For instance, in certain cases it can be desirable to trim the web structure such that a metallic cable is within a predetermined distance from the side edge of the web structure. This allows web structures to be joined together along the side edges during formation of the tire. An anomaly can occur if the web structure is improperly trimmed such that a metallic cable is either too close or too far away from the side edge of the web structure.
Existing techniques are known to examine a web structure for anomalies as the web structure leaves the calender. For instance, one known technique makes use of cameras designed to capture visible light images reflected off of the web structure as it leaves the calender. The visible light images captured by the camera can be analyzed to determine the presence of an anomaly, such as missing rubber material over a portion of the web structure. This technique requires the use of expensive high resolution cameras and requires stringent lighting requirements. Moreover, this technique cannot be typically used to detect an out of place or missing cable anomaly or an improper edge trim anomaly in the web structure.
Another known technique makes use of x-ray and beta particle scanners that examine the web structure as it leaves the calender. These systems require very expensive scanning equipment and can be used to detect anomalies such as a missing or out of place cables and improper edge trims, but are not typically suitable for detecting anomalies such as missing rubber material over a portion of the web structure.
Thus, a need exists for a relatively low cost solution for inspecting a web structure as it leaves the calender. A system and method that can detect anomalies such as missing or out of place metallic cable anomalies, improper edge trim anomalies, and missing rubber material anomalies would be particular useful.